The method is an integration between practice oriented study and institutional grammar tool that is useful to elicit rules underlying farmer-led collective trading that are usualy unwritten. The article is equipped with steps to elicit unwritten rules and with examples of actual smallholders' collective trading. The integrated method is relevant for researchers or development interventionists in revealing institutional nature of food markets that operate unwritten rules-in-use or a blend of written and unwritten rules-in-use. The data used for analysis this paper is stored in Wageningen University. Due to the sensitivity of the data, the data is not made available for public.